In the recombinant screening program during the past year, we screened approximately 5,000 mice for crossing over, mutation and genetic variation. We picked up 10 new recombinants. The recombinants were established as congenic inbred strains and made available to outside laboratories. We extended our studies in gene complementations to show all of the possible allelic combinations which can generate new I-region gene products capable of antigen presentation. By using an Ia mutant, we were able to show that Ir genes, MLR determinants and Ia antigens are coded by the same gene. In the past year, we have also shown that Ia molecules mediate autoimmunity in the case of myasthenia gravis. We have established a model for rheumatoid arthritis in mice and have mapped the genes involved with the I region. We have generated MHC-restricted T-cell clones against determinants on a parasite antigen (Trichinella spiralis) and the alpha and beta chains of human hemoglobin. We have also generated monoclonal antibodies against the same determinants. We will be producing anti-idiotype to these reagents to regulate their immune responses.